Sources familiar with the deal say the company, which is a subsidiary of New York Life Insurance, will take the nearly two million square foot tower’s entire 43rd and 44th floors. Together, the two floors total about 60,000 square feet sources say.

1345 Avenue of the Americas

The space is being offered for sublease by the financial company Alliance Bernstein, which occupies hundreds of thousands of square feet at the property. Rents in the deal, according to sources, are in the $70s per square foot. The term of the transaction, which may depend on Alliance Bernstein’s own lease expiration, was unclear as of press time.

The Mackay Shields deal appears to be for rents less expensive than another sublease at the property just months ago. In October ION Trading, a financial firm, took the top two floors at the property, 49 and 50, which total about 60,000 square feet, for rents in the $80s per square foot. ION subleased the space from another tenant, the German insurance company Allianz.

Though the floors are higher than the ones Mackay Shields is taking and may command a slight premium, the difference in rents could also be a sign of the current market, which has seen a dramatic dip in activity in the first quarter of the year.

Mackay Shields will be stepping away from one of the city’s most exclusive but expensive office buildings, 9 West 57th Street, an office tower owned by the enigmatic landlord Sheldon Solow. Rents at 9 West rise well into the $100s per square foot with prime spaces, such as the building’s top floor, breaking past $200 per square foot, one of the most expensive rental rates in the city that only a small handful of elite office buildings are able to charge.

A CBRE team led by one of the company’s top executives and dealmakers Robert Alexander is handling the sublease assignment for Alliance Bernstein. None of the brokers could be reached for comment. Fisher Brothers Management owns 1345 Avenue of the Americas but was not directly involved in the sublease deal.